Redistribution of moisture and ions in cement based materials
type: CreativeWork
description: There were two principal objectives for this thesis. The first was to develop a methodology and evaluation model of moisture redistribution in order to make the future relative humidity in a screeded concrete slab predictable. The second objective was to develop a method to determine the critical humidity for ion transport in concrete. Residual moisture in screeded concrete slabs may be redistributed to the top screed surface under a semi-permeable flooring, thus elevating the relative humidity, RH, and possibly exceeding the critical humidity level. Passing the critical humidity level may result in material damage to the flooring and adhesive. In order to avoid such damage there is a need of a methodology to estimate the maximum humidity obtained underneath flooring. The redistribution of residual moisture may increase the concentration of alkali at the contact area between the adhesive and concrete. This alkali increase may initiate and sustain adhesive deterioration, which is a common moisture related damage. Several screeded concrete slabs with PVC flooring were prepared to reproduce and monitor moisture distribution and the subsequent redistribution. The moisture distribution before flooring and after a certain period of redistribution is presented. In addition, sorption isotherms including scanning curves were determined in a sorption balance for materials used in the floor constructions, viz, w/c 0.65 concrete, w/c 0.4 concrete, w/c 0.55 cement mortar, and Floor 4310 Fibre Flow, a self levelling flooring compound. Repeated absorption and desorption scanning curves starting from the desorption isotherm were also investigated. The measurements performed made it possible to develop both a qualitative and quantitative model of moisture redistribution and to quantify the humidity achieved under the flooring. The hysteresis phenomenon of the sorption isotherm is considered in the model. The model is well suited for estimations of the future RH underneath flooring i…
abstract: There were two principal objectives for this thesis. The first was to develop a methodology and evaluation model of moisture redistribution in order to make the future relative humidity in a screeded concrete slab predictable. The second objective was to develop a method to determine the critical humidity for ion transport in concrete. Residual moisture in screeded concrete slabs may be redistributed to the top screed surface under a semi-permeable flooring, thus elevating the relative humidity, RH, and possibly exceeding the critical humidity level. Passing the critical humidity level may result in material damage to the flooring and adhesive. In order to avoid such damage there is a need of a methodology to estimate the maximum humidity obtained underneath flooring. The redistribution of residual moisture may increase the concentration of alkali at the contact area between the adhesive and concrete. This alkali increase may initiate and sustain adhesive deterioration, which is a common moisture related damage. Several screeded concrete slabs with PVC flooring were prepared to reproduce and monitor moisture distribution and the subsequent redistribution. The moisture distribution before flooring and after a certain period of redistribution is presented. In addition, sorption isotherms including scanning curves were determined in a sorption balance for materials used in the floor constructions, viz, w/c 0.65 concrete, w/c 0.4 concrete, w/c 0.55 cement mortar, and Floor 4310 Fibre Flow, a self levelling flooring compound. Repeated absorption and desorption scanning curves starting from the desorption isotherm were also investigated. The measurements performed made it possible to develop both a qualitative and quantitative model of moisture redistribution and to quantify the humidity achieved under the flooring. The hysteresis phenomenon of the sorption isotherm is considered in the model. The model is well suited for estimations of the future RH underneath flooring i…
author: Åhs, Magnus
language: eng
keywords: Materials Engineering, Moisture redistribution, ion redistribution, cement based materials, hysteresis, sorption isotherm, scanning
date published: 2011
date modified: 2026-07-24T02:59:49Z
provider: University of Lund
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Division of Building Materials, LTH, Lund University